This review is a compilation of the green synthetic methods used in the synthesis
of coumarin derivatives. Coumarins are a class of compounds with a pronounced wide
range of biological activities, which have found their application in medicine, pharmacology,
cosmetics and food industry. Their biological activity and potential application are
highly dependent on their structure. Therefore, many researchers have been performing
the synthesis of coumarin derivatives on a daily basis. High demands for their synthesis
often result in an increased generation of different waste chemicals. In order to minimize
the utilization and generation of toxic organic substances, green synthetic methods are applied
in this manner. These methods are getting more attention in the last few decades.
Green chemistry methods cover a wide range of methods, including the application of ultrasound
and microwaves, ionic liquids and deep eutectic solvents, solvent-free synthesis, mechanosynthesis
and multicomponent reactions. All typical condensation reactions for coumarin synthesis like Knoevenagel,
Perkin, Kostanecki-Robinson, Pechmann and Reformansky reactions, have been successfully performed using
these green synthetic methods. According to the authors mentioned in this review, not only these methods reduce
the utilization and generation of toxic chemicals, but they can also enhance the reaction performance in
terms of product yields, purity, energy consumption and post-synthetic procedures when compared to the conventional
methods. Due to the significance of coumarins as biologically active systems and the recent demands
of reducing toxic solvents, catalysts and energy consumption, this review provides a first full literature overview
on the application of green synthetic methods in the coumarin synthesis. It covers a literature search over
the period from 1995-2019. The importance of this work is its comprehensive literature survey on a specific
class of heterocyclic compounds, and those researchers working on the coumarin synthesis can find very useful
information on the green synthetic approaches to their synthesis. There are some reviews on the coumarin synthesis,
but most of them cover only specific reactions on coumarin synthesis and none of them the whole range
of green chemistry methods.
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